Tone arm retaining device



Aug. 1951 G. M. PFUNDT 2,998,255

TONE ARM RETAINING DEVICE Filed Dec. 20, 1957 United States Patent 2,998,255 TONE ARM RETAINING DEVICE George M. Pfundt, Bustleton Pike, Churchville, Pa. Filed Dec. 20, 1957, Ser. No. 704,140 Claims. (Cl. 274-1) This invention relates to phonographic machines for reproducing records. More particularly, the invention deals with a device for engaging and definitely retaining a tone or pickup arm against movement in the cabinet regardless of the position of the cabinet in the handling thereof.

The novel features of the invention will be best understood from the following description, when taken together with the accompanying drawing, in which certain embodiments of the invention are disclosed and, in which, the separate parts are designated by suitable reference characters in each of the views and, in which:

FIG. 1 is a diagrammatic perspective view of the upper portion of the cabinet of a phonographic machine, illustrating the use of my improved devices in retaining a tone arm against movement, parts of the construction being broken away and in section;

FIG. 2 is a sectional side view of part of the structure, as seen in FIG. 1, on an enlarged scale and diagrammatically showing in dot-dash lines, the method of attaching and detaching an arm with the retaining device.

FIG. 3 is a partial plan view of the structure seen in FIG. 2 also indicating in dot-dash lines the manner of at tac-hment and detachment of the arm; and

FIG. 4 is a perspective view of one of my improved devices detached and indicating in dot-dash line its assm ciated lock element part.

.With phonographic machines of the type and kind under consideration and particularly with the portable type of machine, it is desirable to retain the tone or pickup arm against movement in the cabinet and, for this purpose, I have provided a retaining device comprising an L-shaped lock element fixed at a suitable position to the forward free end portion of the arm and a coupling assemblage 11 of the retaining device suitably fixed to a part of the cabinet of the machine.

In illustrating one adaptation and use of my invention, I have shown in FIG. 1 of the drawing the upper portion 12 of a phonographic machine having a recessed top wall portion 13, a hinge cover indicated in part at 14. At 15 is a rotatable table having a protruding center pin 16 for positioning of a record thereon, the record being diagrammatically illustrated at 17. At 18 is illustrated the upstanding post of a tone arm 19 and, in the construction shown, the lock element 10 is fixed to one side of the free end portion of said tone arm as diagrammatically illustrated.

Again, in illustrating one adaptation and use of my invention, the assemblage 11 of the device is fixed to the wall 13 at a position to register with the element 10 as later described. The element 10 is in the form of an L-shaped plate defined by angularly disposed walls 20 and 21, the wall 20 being apertured to receive a fastening screw or other device 22, and this wall is also cut out, as seen at 23 in FIG. 2 of the drawing, to form a downwardly extending tongue 24 which acts as a key engaging the lower surface 19' of the arm 19 in preventing rotation of the element 10 on the arm. The wall 21 of the, lock element 10 has side edges recessed to form a neck portion 25, the neck being partially formed by outwardly flared side edges 26 on said element, as best noted in FIG. 3 of the drawing. It will be understood that the tongue 24 becomes a downward extension of wall 21.

The assembly 11 comprises a more or less L-shaped receiving bracket 27, the bracket having a short wall 28 apertured to receive fastening or mounting screws 29 and I a long wall 30, the free end of which has a notch or socket 31 bordered by a short extending wall portion 32' and a long tongue-like wall portion 33 preferably having a curved inner surface 34, as clearly noted in FIG. 2 of the drawing.

The member 36 is generally of channel cross-sectional form or, in other words, defined by irregularly shaped side plates 37 joined by a crosshead 38. The plates 37 s are contracted toward their free end portions and these: end portions include projecting parallel'fingers 39 so sitioned as to pass freely but snugly over the lock ele}:

ment 10 or the wall 21 thereof when the device is in operative position, as diagramatically illustrated in FIG. 4 of the drawing. In this position, the wall 21 of the ele ment 10 is disposed in the notch 31 with the neck portion 25 in alignment with the tongue 33, as will appear from a consideration of FIG. 3 of the drawing. It will be apparent that the notch 31 retains the element 10 against movement longitudinally with respect to the length of the arm 19, whereas the fingers 39 prevent displacement of the element 10 in the direction of the arrow 40 of FIG. 2. It will also be understood in this connection that the neck portion 25 also prevents movement of the arm 19 in the direction of the arrow 40 of FIG. 3.

In order to insure positive retention of the member 36 in its operative position, as seen in FIG. 4 of the drawing, a spring has its coil portion 41 arranged on the pin or rivet 35, note FIG. 4. One end of the spring is fixed to the lower portion of the wall 30, as seen at 42, whereas the other end of the spring is mounted in the plates 37 adjacent the crosshead 38 as indicated at 43, the spring normally maintaining the member 36 in its operative position as seen in FIG. 4 of the drawing. It will also appear from a consideration of FIG. 2 of the drawing that one side of the wall 30 is notched as seen at 44 to clear the spring end 43.

In order to detach the arm 19 to position the same for reproducing use on a record, the member 36 must first be depressed, as diagrammatically illustrated by a finger of one hand in FIG. 2 of the drawing, while manually raising the arm in the direction of the arrow 40, as also diagrammatically illustrated in FIG. 2, to withdraw the element 10 from the notch 31 and also from displacement with respect to the tongue 33. In replacing the arm 19 in its retained position in the device the above operation is reversed. In other words, the member 36 is depressed to clear the notch 31 for reception of the neck portion 25 of the element 10, whereupon the arm 19 can be moved to position the neck portion of the element 10 properly in the notch 31, whereupon pressure is released from the member 36 and the spring will automatically move said member into the operative position as illustrated in FIG. 4 of the drawing.

I claim:

1. In phonographic machines, a tone arm retaining device comprising a lock element fixed to and projecting outwardly from the free end portion of a tone arm, a coupling assemblage fixed to the cabinet of the machine in registering alinement with said element, said assemblage comprising a stationary L-shaped bracket, a member of channel cross-sectional form, a pivot pin and a spring, said bracket and element having cooperating means for retaining the tone arm against swinging movement, said pivot pin pivotally supporting said member on the bracket with a part of the bracket arranged in the channel of said member, said member having means operatively engaging said element and said part of the bracket in retaining said arm against vertical movement, and said spring being mounted on said pin and opera- Patented Aug. 29, 1961 v 3 tively engaging said'member to normally retain the same in operative position.

2. A device as defined in claim 1, wherein said member includes a portion. extending above said. last named means,. and said portion facilitating manual movement ff'saidj member intoinoperative position" against the ace tionoi said spring in couplingand uncou 1ingsaid-element 'with said bracket.

3 ..A device as defined in claim 1, wherein". said coogeratingmeans comprises a notch in saidpart of'the bracket, and 'a' neck portion on said *elementadapted to; seat in said'notch.

A device as defined in claim 3, wherein the-'means' on said member comprises a pair of fingers'adaptedto overlie the neck portion of said element seated, in said notch in retaining the elementagainst displacement from said notch.

5. A device as defined in claim 4, wherein said part of-the bracket-has at one-'side-of thenotch an upwardly extending tongue-like portion, and said tongue-like portion having a curved surface for guiding the element into said notch.

References Cited in the'file of this patent UNITED STATESEPATENTS 1,439,324 Petersen Dec. 19, 1922 1,704,260 Rodriguez Mar. 5, 1929 1,732,067 Samuel Oct.- 15, 1929 1,974,070 Hibbard Sept. 18, 1934 2,254,732 Dally Sept; 2, 1941 FOREIGN PATENTS 161,670 Australia Mar. 3, 1955, 759,313- Great Britain Oct. 17, 1956 

